u6 Flashcards
earths surface is heated unevenly because of…
rotation of earth, land and oceans, seasons
heat is moved around the earth via ________
water vapour
atmosphere is ___% nitrogen , ___% oxygen and ___% other
78% N
21% O
1% other
give layers of earth from land to space direction
troposphere, stratosphere, mesosphere, thermosphere, exosphere
what is the definition of “lapse rate”
how much the temperature changes over a given height
why does the tropopause shrink near poles but high near equator?
because equator = hot air rising expands it
lapse rate of troposphere
lose 2ºC of termerparte per 1000 ft height
the average temp of tropopause is _____ and the temp remains _______
-56ºC
isothermal (doesn’t change)
the stratosphere height in ft and km
lapse rate/temperature _______,
weather can’t penetrate further than this layer because of _________
180 000 ft
50 km
increases to 0º because of heated ozone layer
lack of convection
mesosphere height in ft and km
it has a ____ lapse rate
what type of molecules are found here
180 000 to 275 000 ft
50-80 km
positive (temp decreases with height)
light gases
thermosphere height starts at
____ lapse rate
why high temperatures?
100 km
negative (temp increases with altitude)
intense solar radiation
exosphere height
pressure is like a ________
500 km onward
vacuum
standard atmosphere (ISA)
pressure
temperate
pressure decrease per 1000 ft
termparteu decrease per 1000 ft
moisture?
rain?
29.92 inHg
15ºC
- 1 inHg drop per 1000 ft
- 2ºC drop per 1000 ft
dry air mass
no precipitation
what is station pressure
does a low or high altitude station have higher pressure
weight of the column of air extending upwards from station to atmosphere
low altitude because more air molecules within column
what is mean sea level (MSL) pressure
pressure of high altitude airport as if it was at sea level
what are isobars and why are they drawn on a map
they are drawn to be _____ hectopascals apart
connect locations of equal pressure
4 hectopascals
isobars close together = _____ pressure difference = _____ flow of air
large
fast
high pressure centre:
- air is ______
- flow/rotates:
- weather:
sinking
rotates clockwise and outward (anticyclone)
good weather
low pressure centre:
- air is ______
- flow/rotates:
- weather
rising
counter clockwise and inward (cyclone)
bad
what is a trough
elongated area of low pressure
what is a ridge
longed area of high pressure
what is a col
natural reaction between two highs and two lows
from high to low lookout below
what does that mean in terms of TEMP difference
temp decrease = air density increases and contracts = don’t need to fly as high to get same amount of lift = plane feels like its at xx height at lower true altitude
so flying from high to low temperature, plane will naturally descend because it feels like its at same altitude as before
from high to low lookout below
what does that mean in terms of PRESSURE difference
high pressure to low pressure = air density decreases
so staying at same true altitude, your altimeter will feel like you’re higher than you acc are in the low zone
obstacle clearance?
altimeter setting vs mean sea level (MSL) pressure
what do you use each for
altimeter setting = current atmospheric pressure reduced to sea level - for setting plane altimeter
MSL pressure = average pressure reduced to sea level over a period of 12h - for flight planning and weather purposes
colder than standard temperature puts the plane _____ than the altimeter says
lower
for every ___ºC temperature change, we change density altitude by 1000 ft
8ºC
heating of the atmosphere by
radiation and conduction
heating of the atmosphere by
radiation and conduction
variations in heating: diurnal variation, seasonal variation, latitude and topography
diurnal variation - day (convection currents rise/mixing atmosphere). night (cooling)
seasonal variation - earth tilt = different heating throughout year
latitude = most heating at equator
topography = land heats up faster than water
variations in heating: diurnal variation, seasonal variation, latitude and topography
diurnal variation - day (convection currents rise/mixing atmosphere). night (cooling)
seasonal variation - earth tilt = different heating throughout year
latitude = most heating at equator
topography = land heats up faster than water
3 ways heat is moved around through the atmosphere
conduction
convection
advection
how does compression of air molecules make the surrounding air warmer
when a large parcel of air sinks, its compressed by the increasing air pressure of the lower atmosphere
increased pressure = the air warms up
3 ways the atmosphere cools
(lack of) radiation = surface cools
advection
adiabatic cooling
dry adiabatic rate
3º per 1000 ft
saturated adiabatic rate
1.5º per 1000 ft
what is a temperature inversion, what causes it and is it stable?
when the temperature increases with altitude
caused by radiation cooling from the surface at night
stable
what is an isotherm on a map
join places of equal temperature on map
the amount of water vapour that air can hold is controlled by the air’s _____
temperature
what is the dew point
termperature at a given pressure that the air must be COOLED to in order to reach 100% saturation
tells us how much water the atmosphere is currently holding
cold or hot air holds more moisture and why
hot because more space for water molecules to fit
what is the relative humidity (%)
the amount of water vapour present in the air compared to the amount that this air can hold when its saturated
dry vs saturated air has ____% relative humidity
dry air = 0% relative humidity
saturated air = 100% relative humidity
cooling or adding moisture will ______ relative humidity
increase
standard vs environmental lapse rate difference
both are the rate that the temperature changes as altitude increases but standard is theoretical (2º/1000) whereas environmental is measured and changes daily
frontal vs orographic vs conventional rainfall
frontal = two air masses/fronts converge
orographic = warm air forced over mountain and cools and rain
conventional = ground surface is locally heated so it rises cools and rain
sleet/ice pellets vs freezing rain
ice pellets = snow drops into warm zone -> melts to rain -> drops in large cold zone -> freeze to ice
freezing rain = snow drops into warm zone -> melts to rain -> passes through a very shallow cold zone but doesn’t have time to completely re-freeze so it stays as rain
sleet/ice pellets vs freezing rain
ice pellets = snow drops into warm zone -> melts to rain -> drops in large cold zone -> freeze to ice
freezing rain = snow drops into warm zone -> melts to rain -> passes through a very shallow cold zone but doesn’t have time to completely re-freeze so it stays as rain
hail is frozen rain drops larger than _____
5 mm
if the dew point is above freezing, _____ forms
if the dew point is below freezing, _____ forms
(dew vs frost)
dew
frost
why does dew/frost form
on a moist day, if the ground cools the air will reach it’s saturation point and need to remove excess moisture
why will a parcel of moist air rise faster than a parcel of dry air
moist air has a smaller adiabatic lapse rate than dry adiabatic lapse rate. so the difference between the environmental lapse rate and SALR is larger than ELR and DALR. since there’s a larger temperature difference with the moist air, it will rise quicker
T/F: the atmosphere is unstable when the environment cools down faster than a parcel of air
true because the parcel of air will keep rising since the environment is colder than the parcel and the hot parcel will rise
stable air:
____ flying
____ visibility
____ precipitation
_____ cloud
____ environment lapse rate
cause _____
smooth
poor
steady
layer/stratus
shallow
inversions
what increases stable conditions
surface cooling
warming at higher altitudes
unstable air
____ flying
____ visibility
____ precipitation
_____ cloud
____ environment lapse rate
can lead to _____
bumpy
good
showery
cumulus
steep
thunderstorm
the greater the ELR, the more atmospheric ______
instability
absolute stability
a parcel of air attempts to rise but will always be colder than the air surrounding it
DALR and SALR are steeper than ELR = air sunk
conditional stability
stability depends on whether air is dry or saturated
only when the parcel of air is saturated it can rise
DALR is steeper (colder) than ELR = air sunk
SALR is shallower (warmer) than ELR = air rises
absolute instability
parcel of air is always warmer than the outside temp so it always rises
DALR and SALR are shallower (warmer) than ELR = air rises
potential instability
air is initially cold/stable and environment is warm so it’s not moving. whacky weather triggers at 5000 ft and all of a sudden the environment is extra cold so now the cold air parcel is under colder outside air so that air parcel rises
what is solar wind
outermost particles of the sun escape the suns gravity and interacts with earth atmosphere -> northern lights
what are sun spots
high energy zones on suns surface that appear dark
what are solar flares
occurs when the sunspot releases huge amount of energy
the earth’s tilt is ___º and the tilt is responsible for what
23.5º
changing seasons
equinox vs solstices
equinox = day and night is the same length
solstices = day or night is the longest during the year
what is light spreading
sunlight in the winter is spread over a large area because the sun passes through the atmosphere at a lower angle = less heat received by earth per square inch
what is atmospheric scattering
as sun passes through atmosphere, particles of gas and dust scatter the light
most scattering near poles = less light directly hits surface
least scattering at equator because direct hit
why is the north pole always cold
- near winter, earth tilt makes it so that only a few hours of light a day
- more light spreading
- more atmospheric scattering
“SKC”
sky clear
FEW clouds
1/8 to 2/8 sky covered
SCT clouds cover
3/8 to 4/8 of sky
BKN clouds cover
5/8 to 7/8 of sky
ceilings exist when sky is _____ or _____
BKN or OVC
lenticular clouds
- from mountain waves
- flat
- top of mountain wave: air rises = cold = condense int
rotor clouds
- formed by _____
- air is _____
mountain waves
violent/turbulent
a cap cloud forms over the top of the mountain and extends partially down the leeward slopes. this indicates…
a strong downdraft
